The present invention relates to a power steering system for vehicles, and more particularly to a power steering system for vehicles provided with a variable discharge type fluid pump.
The system of this kind generally includes a steering mechanism for transmitting rotation of a steering shaft of a vehicle to a piston shaft of a power cylinder to operate wheels and a variable discharge type pump driven by a prime mover to generate pressure fluids, whereby the pressure fluid from the pump is selectively supplied to one of both cylinder chambers of said power cylinder to aid rotation of said steering mechanism.
U.S. Pat. Nos. 3,931,711 and 3,996,742 disclose a mechanism in which a discharge amount of pressure fluid generated per unit operating stroke by a pump is controlled in response to the steering torque or steering speed. This mechanism is in response to fluid pressure on the upstream side of a throttle which varies in opening area in response the steering torque or steering speed generated in the steering mechanism.